Builders will sometimes break the pattern in the center of the garage like above where 24" centers are on each side of the 12" on center.

When the carrier lacks clearance above it the totes can be loaded from both sides, allowing carrier to run between the totes as illustrated..

​Your layout of your system is dictated to a large extent by the joist locations or distance from walls or garage door opener carrier. When access by a crawl space is available (not available when living space is above garage) it is possible to lay lumber over existing joists so they can be placed where you want the system to go or, allowing for 24 totes with a hip roof, etc. (6"screws extend into 2x4's)